Reproducible Plasmonic Nanopyramid Array of VariousMetals for Highly Sensitive Refractometric and Surface-Enhanced RamanBiosensing

摘要

Localized surface plasmon resonance (LSPR) biosensors show great potential for practical/commercial use in clinical diagnosis, home healthcare, environmental analysis, and public healthcare. However, two main issues, that is, low refractometric sensitivity and low reproducibility (large-area uniformity and batch-to-batch consistency), hinder the extensive applications of LSPR biosensors. Therefore, plasmonic nanostructures with high sensitivity and excellent reproducibility are desirable for preparing reliable LSPR sensors. Herein, we have fabricated plasmonic nanopyramid arrays (NPAs) for several batches with reproducible morphology and optical properties by elastic soft lithography and metal thermal evaporation. NPAs of various metals (i.e., Al, Au, and Ag) were also prepared by thermal evaporation with the according metals. The transmission spectra of these NPAs showed several narrow LSPR peaks in the visible-infrared wavelength region. The refractometric sensitivities of the LSPR peaks were systematically studied, and high refractometric sensitivities of 774.0, 472.8, and 421.0 nm/RIU were achieved on Al, Au, and AgNPAs, respectively. To demonstrate the potential of the NPAs for multiplexapplications, we first applied this highly sensitive Al NPA biosensorto monitoring the process of proliferation of HeLa cancer cells, insitu and in real time. Then, we demonstrated that the Au NPA wasable to identify the absorbed analytes on its surface through thesurface-enhanced Raman scattering spectrum. In addition, the finitedifference time domain simulations were performed to reveal the electromagneticfield enhancement on NPAs. Because of the properties of high sensitivityand excellent reproducibility of the metal NPA LSPR substrates, aswell as the simplicity and cost efficiency of the fabrication method,our proposed work will accelerate the practical use of LSPR sensors.